ns1.bul.net has no MX records.
Question and response
Question
dig ns1.bul.net. MX
Answer
The response has no answer records.
Authority
bul.net. 3600 SOA bsh1.bul.net. noc.bul.net. 2024010775 10800 3600 604800 86400
Additional
. 0 OPT ; payload 1680, xrcode 0, version 0, flags 0